1. Technical Field
The present invention relates generally to simulation tools for mainframe computers, and more specifically relates to a method for modeling LPAR behaviors within a mainframe simulation tool.
2. Related Art
A logical partition (LPAR) is the division of a computer's processors, memory and storage into multiple sets of resources so that each set of resources can be operated independently with its own operating system instance and applications. The number of logical partitions that can be created depends on the system's processor model and resources available. Typically, partitions are used for different purposes such as database operation or client/server operation or to separate test and production environments. Each partition can communicate with the other partitions as if the other partition is in a separate machine. Both of IBM's® z/OS and AS/400 products support logical partitioning. HITACHI® and SUN MICROSYSTEMS® also use forms of logical partitioning.
Often it is necessary to model the performance of mainframe systems utilizing LPARs, e.g., to meet customer needs, etc. Unfortunately, current modeling techniques do not account for various LPAR behaviors. One such behavior involves time slice dispatching, which occurs when the total processor consumption nears 100%. Time slice dispatching, as opposed to event dispatching, refers to the way physical CPs (central processors or central processing units) are dispatched to logical CPs by the dispatcher. Because time slice dispatching has an impact on the workload performance of the system, it must be accounted for.
Another behavior involves the interaction of several LPARs running on the same processor. In an LPAR mode configuration, the performance of workloads running in one LPAR can be heavily affected by the work running in other LPARs. This is especially true when the total utilization of the processor approaches 100%. Since known simulators generally only model the workloads in one LPAR at one time, the workloads running in the other LPARs are defined as a constant amount of capacity (i.e., some number of MIPS). However, this assumes the amount of capacity used by these other LPARs is fixed or constant. In real systems, the amount of capacity used by these other LPARs is variable and is a function of the capacity used by the LPAR being modeled.
Accordingly, a need exists for a simulation tool that can better model LPAR behaviors.